A Year in the Making!

Today is the one year anniversary of the start of my little experiment.... the "Rants from the Embedded Hardware Guy" blog.

It has been so much fun building up projects and taking pictures to meet my "imaginary" personal deadlines, so I can share them on this blog. I would encourage anyone who likes too, or wants too, tinker at home to start a Blog and post your projects. Creating an account on BlogSpot and posting videos on YouTube is free, it just takes a little bit of time.

This Blog has reignited my "Hacker/Maker" drive and has connected me with Engineers all over the world. I have appreciated all the feedback I have received about my posts and love being a part of the Open Hardware sharing community.


Like most Bloggers I am obsessed with my blogs stats (page views, traffic sources, and audience), but one of the neat side benefits is getting to see what web browsers and operating systems are being used to view the blog:

 (Microsoft is in control, but I thought it was interesting that Linux and Mac are both about the same usage in the Engineering community.)


Thank you for a great year and I hope for many more to come!

Free Beer..... Today at Arrowfest!

I just got back from my yearly trek up to Minneapolis, MN USA to attend Arrowfest. For those of you not familiar with Arrowfest, Arrow is one of the top 3 Electronic Component Distributors in the world and once a year they put on a large event called Arrowfest. The event consists of 24 different technical seminars during the day (you pick 4 you are interested in) and a tent exhibition with vendor booths, free swag giveaways, drawings for prizes, free food, and yes free beer (And a handy Arrowfest Glass Mug to put it in.)

My wife gives me a bit a grief for continuing to fill our kitchen cabinets with Arrowfest mugs (I think I am up to 10 or 11 now). They make great beer & coffee mugs though!

I am a pretty firm believer in you get what you pay for when it comes to technical training seminars. If you attend a 2-day seminar and it costs you $1,500 to attend it is probably going to be a lot more in depth and worth wild than a free 1.5 hour seminar.... that being said, I do enjoy the Arrowfest technical seminars, and appreciate that they hand out the slides (on a CD) so I can check out the other 20 classes that I had to miss.

The Exhibition Tent is worth wild as well; there were booths from more than 85 different electronic component manufacturers and sales representatives all showing off there latest and greatest products. The big guys Texas Instruments, National Semiconductor (aka Texas Instruments), Linear Tech, Analog Devices, Altera, Freescale, Atmel were there along with many other manufactures. They were also handing out a ton of SWAG!

My Daughters love it when I go to these things, because it is like Christmas when I get home. My favorite swag had to be the Analog Devices Tape Measure, the Atmel pocket knife, and the Kemet Vertical Phone holder (that blue and white thing on the right). I also collected 3 or 4 aluminum tins of mints.... more project hacks coming up I guess :)

I don't make it up to too many training seminars  nowadays, but I always try and make it up to Arrowfest. It is great getting all the reps and manufacturers under one roof and I always run into old coworkers or friends in the industry. Plus a few years ago I got to meet Bob Pease at my local Arrowfest (Very Cool!) ...... I met Dave Van Ess at Texas Instruments Tech Days a few years ago too (a very close second, Very Cool!)


And just in case my Boss is reading this blog post... Yes I did find some cool stuff we could use on future products and I got a few pending questions answered... Thanks for paying for my gas :) 

Just Fooling Around with Logic..... don't tell my Wife!

It's Friday night and my wife and girls (a 4year old and 20month old) are off visiting relatives and I am trying to work out some concepts for my entry into the Open 7400 Series Logic design competition.....

I thought I'd just start with the basics and work my way up. Every Logic based design needs a clock, so I started out building up a 1Hz Ring Oscillator with a 74HC04. (The LTSPICE Yahoo Groups had this great Ring Osc. circuit which I used as a starting point).

Then I thought using a 74HC90 BCD Counter to drive a 74LS47 BCD to seven segment driver would be a fun way to use a 1Hz clock.... pretty Digital Logic 101, but hey I need to start some where.

So here is the first "Brain Storming" part of my entry:

Much more circuitry and trickery to come before the deadline!

Low Cost Misc Parts Kits

Back when I started messing with electronics as a teenager I started a misc parts bin of resistors, capacitors, LEDs, 555 timers, 7400 logic parts, etc. for my projects. Within a few years that bin grew to a box, to many boxes and now I have a parts closet at home; with each shelf sectioned off for Caps, Inductors, Resistors, Connectors, ICs, etc.

While searching on ebay for used Test Equipment (another addiction of mine) I came across these neat parts kits.
SMT Voltage Regulator Engineering Kit w/ SMT PCBs
Analog IC DIP-Only Design Kit #1 (#1120)
Master Op Amp IC Design Kit #1 with PCB (#1565)
Linear IC DIP-Only Design Kit #2 with PCB (#1310)

There are many more kits at Night Fire's ebay store: http://stores.ebay.com/nightfireelectronickits

Even though I have a closet full of parts at home sometimes getting a small bag of parts stirs my imagination enough to think of my next hack. I just received the Master Op Amp kit and I am ready to build something up!

Simpson Multimeter Clock

Lauro posted a link to this awesome project on the blog and it is so cool I needed to share it. It is a Simpson Multimeter Based Clock.

Overview:

The Multimeter Clock consists of three multimeters, the first meter displays hours, the second displays minutes and the last displays seconds. A 16F628A PIC microcontroller keeps track of time and outputs a calculated current to each meter to display the current time.

Here is a link to the Project Page.

 This is a very cool project and a neat twist on making a clock!

Fun with Filters!

A couple weeks ago I built a simple 1KHz 6Vpp Sine Wave Generator from a handful of opamps and passives I had laying around. You can check out that project here.

I thought it would be fun to quantify just how good of a Sine Wave this circuit was; after all it was just a wave-shaped triangle wave, so I wasn't expecting  too much. But if I quantify how good of a sine wave it is I can tweak the circuit to try and make if better.

Since my Sine Wave is at 1KHz I thought I'd measure its quality using an audio Total Harmonic Distortion (THD) technique.

Essentially, a perfect sine wave should only have a single frequency component at the fundamental frequency, but real sine waves have harmonic distortion. This harmonic distortion is the part of the sine wave that we really don't want; a poor sine wave has lots of harmonic content and a good sine wave has little to no harmonic content. So if we measure the amplitude of the harmonics we can quantify how good our sine wave is!

What we need to do is design a Notch filter at 1KHz. This will remove the fundamental frequency and leave the Harmonic content. Below is an LTSPICE schematic of Sine Wave Generator and Notch Filter.

The next picture is the frequency response of the notch filter; you can see it is centered at 1KHz.

When the 1KHz signal is passed through the 1KHz centered notch filter the fundemental frequency is removed and what is left is the Harmonic content. You can see the 3rd harmonic at ~3KHz is what is left.

(The blue is the signal coming out of the Filter)

Below is the FFT of the input Sine Wave and the Output of the Notch Filter; you can see the fundamental frequency amplitude is lower with minimal effect on the harmonic content.

Now that I had a base line simulation working I grabbed my soldering iron and built up the 1KHz Notch Filter dead bug style in an Altoids box. I wish I had a Network Analyzer or at minimum a Spectrum Analyzer with a tracking output to measure my filters frequency response, but all I had was a function generator and a scope.  I swept the function generator's output frequency from 10Hz to 100KHz and could see that my filter worked well at filtering out 1KHz signals.

(Channel A = Input Signal, Channel B = Output of Notch Filter)

The output of the Sine Wave generator measured 2.25Vrms and the output of the Notch filter was 139mVrms. This gives me a THD of (139mV/2.25V) = 6%

I wanted a second opinion, so I grabbed a HP 331A Distortion Analyzer and set it up. I hadn't used one of these since I interned at an RF Radio Manufacturer back in 2002. I used it to measure receiver sensitivity performance.

I had to dig up a manual to remember how to setup the HP 331A. It is a bit confusing because you have to setup the meter to 100% full scale based on your input, then adjust the frequency & balance adjustments until you get the lowest % THD reading. I monitored the Output of the 331A with a scope to see that I had fully removed the 1KHz fundamental and all that was left was a dirty looking 3KHz waveform (3rd harmonic).

The HP 331A measured a THD of 7.4%; pretty close to my homemade notch filter 6% reading. It makes sense that my filter's THD measurement would be lower, because it probably attenuated the 3rd harmonic a bit more than the much more precise HP 331A's notch filter would do.

Below is a scope screen shot of the output of my notch filter (top) and the output of the HP 331A (bottom).

Both filters did a nice job removing the fundamental and the 3rd harmonic is defiantly the most dominate remaining frequency. This was a fun project and cool to see that my Notch Filter implementation's THD readings weren't that far off from a HP331A's measurements.

Update: Sept. 13th, 2011
 
I thought I would do one last test to see the performance of the Notch Filter on a much cleaner sine wave. I used a BK Precision 3011B to generate an identical (but much cleaner) 1KHz 6Vp-p Sine Wave and used the Notch Filter to measure its THD.

The center frequency of my notch filter looks to be ~1074Hz; that is where I got the best filter performance.

(Top = Input Sine Wave, Bottom = Output of Notch Filter)

The THD measured was (19.5mVrms / 2.25Vrms) = 0.86%, a much cleaner Sine Wave than my home brewed one at 6%.


Here are Links to my LTSPICE files: Sine_&_Filter, Filter, and Filter_ac.

Link to HP 331A Manual.

References:
Distortion Analyzer by Rod Elliott
HP Journal: Distortion Analyzer
Texas Instruments Notch Filter AppNote

Getting my Nerd On!

Check out my cool (EEVblog) 555 T-Shirt my wife got me for my Birthday! She is a keeper!

If I changed the 5K resistors to 560K and put TS1001 next to the comparators, I'd have my contest entry all documented :)

Mounting my Arduino Clock

Alright I lied about not posting about my Arduino Uno based Clock/Temperature Sensor again, but this post is more about the enclosure than the guts. If you are interested in the guts check out my older post: Arduino-Uno-Clock-and-Temperature

If you haven't figured it out by now, I am addicted to mounting electronics in Altoids boxes. They are handy shielded enclosures that are the perfect size for most of my projects and are easy to modify with some sheet metal shears and a few drill bits. Also using these cases feeds my other addiction...... eating mints!

I made a small Dead Bug style PCB for the DS1307 & DS1621 that I soldered to the case; an easy way to keep it from moving around. I thought about putting a CR2032 battery holder in the box, but the battery backup should last greater than 5 years.... so I just soldered a couple wires to it and hot glued it to the lid. In 5 years I'll peel it off and solder up another one.

Now I have a very handy desk clock all mounted up and minty fresh!

How the Transistor Got its Name

I saw this post today from adafruit and it was so cool I needed to republish it.

(Click on the above image to zoom in)

They voted on the name! Pretty cool, if you were on the wining side of the vote..... just to say you got to name the Transistor!

7400 Logic Series Design Contest

I just found this 7400 series Design Contest.

http://dangerousprototypes.com/open-7400-logic-competition/

Entries must be received by October 21, 2011, 6AM GMT. Winners will be announced on November 1, 2011.

Judging criteria and categories

Entries will be judged for:

• Originality. A smart new design that inspires
• Documentation. Schematics, theory, pictures and/or video
• (Mis)use of 7400 logic. Show us what 7400 logic was (never) meant to do
• Technical prowess
• Build quality
• Imagination and creativity

Looks like a lot of fun! Get your solding irons heated up! Below is a link to an ebay sellar that is selling 74HC00 Series Logic kits; a great place to get a bunch of parts for cheap.
http://www.ebay.com/itm/74HC00-02-04-08-32-Assorted-Logic-IC-Kit-fcbusa-/360141624609?pt=LH_DefaultDomain_0&hash=item53da1d1521
Update: Sept. 7, 2011: Just got my 74HC parts, let the project building begin!